1. Field of the Invention
This invention relates to catheterization of a patient, and more particularly relates to an obturator assembly which prevents backflow of blood or other body fluid during a catheterization procedure.
2. Background of the Invention
For many applications, a catheter, after insertion into a patient, must be maintained in place for periods up to two weeks or more. During this time, medication changeovers may be alternated with periods when no solutions are being administered to the patient. It is essential that patency of the catheter be maintained during changeover periods.
In the current state of the art, patency of a vascular access catheter, with or without an attached intravenous drip, is generally maintained in one of three ways. A sterile aliquot of heparin solution may be injected into the catheter. This method, often termed a heparin lock, is costly since expensive heparin may be required for prolonged periods. Alternatively, a sterile bolus of normal saline solution may be injected into the catheter. Both of these methods must be done routinely and often; however, because of normal diffusion at the tip of the catheter, blood may replace infused heparin or saline solutions. A common result is the loss of patency through the formation of a clot near the tip of the catheter. In a third method for maintenance of patency, a stainless steel or plastic obturator may be inserted loosely inside the catheter and attached with a leur connector. These devices are primitive and do not completely seal the catheter so that blood may seep back into the space between the catheter and obturator. This backflow of blood not only may clot and occlude the catheter or interfere with subsequent removal of the obturator, but also is an excellent breeding ground for infection.
Hydrophilic polymers which absorb water and expand, often termed hydrogels, have long been known. Karakelle et al., in U.S. Pat. No. 4,743,629 discloses hydrophilic polyurethane compositions which absorb significant amount of water, expand and allow species soluble in water to permeate through the composition by a partition type permeability process.
Hydrophilic polyurethanes which absorb water and expand have been used to manufacture over-the-needle catheters. These catheters are emplaced in a patient's vein by mounting the catheter by a press fit over a needle or catheter inserter used to puncture the vein. The catheter, due to its hydrophilic nature absorbs water so that its diameter expands releasing the needle and leaving the catheter emplaced and ready for administration of a solution. Exemplary of such over the needle catheters is the disclosure of Luther in U.S. Pat. No. 4,668,221. Luther does not, however, address the problem of maintaining patency of the patented catheter after removal of the needle.
A definite need exists in the art for a reliable, improved and inexpensive method to maintain patency in an indwelling catheter during medication changeovers. The present invention addresses this need.